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Hundreds could die, with thousands more injured. In effect, the wave energy is trapped by the edges of the body of water. This means that the internet, your cell phone, grocery stores, and gas stations may also not work. A lot of people are transplants, Forson said. In the Puget Sound region, it takes a trained eye to recognize rocky outcrops and subtly raised ground as evidence of a fault. endobj 3 0 obj Even if the earthquake is too small to be felt by people, seismographs can detect it. The marshy deposits are about a meter higher at Lake Hancock. Sometimes there may be a layer of volcanic ash or charcoal that has been deformed by the fault. A baristas hand hovers over the bean grinder. In addition, the Survey performs seismic safety evaluations of schools. A thrust fault is a special kind of reverse fault that has a shallow dip. America is going to pay for sitting back doing nothing while almost 70 million babies were slaughtered and their body parts sold to the highest bidder for the last 43 years. Jump from 60 to 600 per week in just 5 years in Pahala, Is the Cascadia Subduction Zone about to blow? As part of the Hazard Mitigation Planning process, mapping of the hazards that have the potential to affect the jurisdiction is performed using geographic information systems (GIS) software. Evidence for Quaternary movement on the southern Whidbey Island fault includes (1) offset and disrupted upper Quaternary strata imaged on seismic-reflection profiles; (2) borehole data that suggests as much as 420 m of structural relief on the Tertiary-Quaternary boundary in the fault zone; (3) several meters of displacement along exposed faults in upper Quaternary sediments; (4) late Quaternary folds with limb dips of as much as ???9?? Earthquakes on faults like these may cause tsunamis in the Puget Sound region. We use cookies on our website to give you the most relevant experience by remembering your preferences and repeat visits. The last major earthquake was over 300 years ago. Reverse faults are usually steep and occur in regions of compression. During the shaking liquefaction occurred, the sand lost its strength, and the car sunk. Many landslide-prone areas of Washington are also located near active faults. Some parts of major cities (including Seattle, Tacoma, and Olympia) have been built on land that was reclaimed from soft and wet tidal ocean areas. This new method allows geologists to see through trees and vegetation to find new faults. The shaking can also cause landslides, surface ruptures, ground cracks, liquefaction, tsunamis, and seiches (standing waves). Other faults may lie entirely underground, or could be covered by vegetation and (or) sediment. Along the water at Cama Beach State Park, cabins on a bluff overlook Saratoga Passage, facing the general direction of Lake Hancock on Whidbey Island. The Seattle fault last ruptured about 1,100 years ago in AD 900950. For several years, scientists pondered where this important regional fault zone continues southwestward from its mapped location in the Everett area. Because Japan was so well prepared, mostretrofitted buildingsoutside of the tsunami zone survived. Move away from buildings, streetlights, and utility wires if you can. A lock () or https:// means youve safely connected to the .gov website. This image shows the how the 1700 AD tsunami from the Pacific Northwest crossed the Pacific Ocean. PO Box 5000 Scientists dont know. The Cascadia subduction zone off the Washington and Oregon coast is capable of some of the largest earthquakes in the world. This map is from a 2007 report on the seismic design categories in Washington. Scientists are not sure how far east it goes. There must be tsunami deposits of the same age along much of the Oregon and Washington coast in order to qualify as an earthquake. They knew something was there, said Sam Johnson, a retired USGS geologist who would follow up on their work. The team also found that accumulated movement on the fault has uplifted old Snoqualmie River sediments to their current position on ridges, in some places several hundreds of feet above the modern Snoqualmie valley floor. Geologists do not yet know how often earthquakes happen on this fault. Here, were looking at one of the bigger faults in the region, he said. For example, the Cascadia subduction zone has had between 15 to 19 earthquakes over the past 10,000 years. An earthquake along the southern Whidbey Island fault reshaped the land some 2,700 years ago. Theres a must-see documentary film called Cascadia The Big One that exposes whats currently going on in this region of the Cascade volcanoes and the Pacific NorthWest. However, we can learn which faults are active and which are inactive. Tsunamis triggered by earthquakes usually require at least a M7 event. The southeastern and central parts of the southern Whidbey Island fault zone form the southwest margin of the Everett basin and northeast boundary of the Seattle basin. This evidence can come from finding something younger than 12,000 years that has been deformed or moved by the fault. All faults, regardless of size, can be dangerous if they rupture. Both of these things can cause equal or greater damage than the actual earthquake. Why is Strange Sounds focusing so much on disaster preps? On an inactive fault, the sea would have risen at the same rate at both locations. stream <> Liquefaction has caused significant damage during earthquakes in Washington. After the earthquake, many things you count on may not be available. Snohomish, King and Island counties would be expected to see the. Do you know what to do if there is an earthquake? During site visits in 2005, Sherrods team found evidence of four SWIF earthquakes in the past 30,000 years. Much of the land along the southwestern part of the lake cracked and subsided. For example, in the open ocean a tsunami may be less than a few feet tall. Customers lift their eyes from phone screens. Hover over a cluster of earthquakes to learn about the different types in the Pacific Northwest. Higher risk areas are in orange and lower risk areas are in green. Transpressional deformation along the southern Whidbey Island fault is indicated by alongstrike variations in structural style and geometry, positive flower structure, local unconformities, out-of-plane displacements, and juxtaposition of correlative sedimentary units with different histories. We do know that it is active and will likely produce a large M67.5 earthquake when it next ruptures. A community meeting about a shelter at the Harbor Inn may have yielded more questions than answers. Like a sonogram, the seismic surveys allowed Johnson to see outlines of massive fissures in the earths crust. This kind of grouping gives us information about how common earthquakes might be and how large an area may be affected. With Medical Martial Law imposed in Washington state. Johnson and others (1996) have described the southern Whidbey Island fault ( figure 1) as a broad (6 - 11 km) transpressional zone comprising three main splays, within which the local late Quaternary uplift rate is at least 0.6 mm/yr. Restoring tap water to some homes could take over a year. Please visit our Geologic Information Portal and Geologic Hazard Maps page for the most up-to-date listing of all of our hazard maps. Every year Western. Deep faults can occur where two tectonic plates collide and one of the plates is forced beneath the other. The fault zone is up to 57 km, correlates with gravity and magnetic anomalies (Finn and others, 1991 #4753; Blakely and others, 1999 #4747), and has been interpreted as a complex zone of transpressional deformation (Johnson and others, 1996 #4751). Necessary cookies are absolutely essential for the website to function properly. Resources on tsunami danger and preparedness in Westport, Grays Harbor County, Long Beach Peninsula, and Coastal evacuation maps. The team determined that the Rattlesnake Mountain fault zone, originally mapped by DNR geologist Tim Walsh in the 1980s, is likely the southern continuation of the southern Whidbey Island fault, extending this fault zone from the Strait of Juan de Fuca to Rattlesnake Mountain near North Bend. For earthquakes that occurred before seismographs were invented, the Mercalli Intensity scale was used to make maps of damage and determine the size and location of an earthquake. Although we know much about active faults and earthquakes, there is much more to learn. The Seattle fault is a good example of a fault that is mostly reverse. Larger crustal faults, such as the Seattle fault and southern Whidbey Island fault zone, can produce earthquakes up to magnitude 7.5. The moment magnitude scale replaced the Richter scale in the late 1970s. A magnitude 7.4 along the southern Whidbey fault would rattle 18 counties in Washington, according to a federal projection . The SWIF was first recognized and mapped at a regional scale by Gower and others (1985) on the basis of gravity and aeromagnetic anomaly maps. Another piece can be seen under the elevated lanes of northbound Interstate 5 in South Seattle not far from the Rainier brewery. They havent dug up enough history to estimate. It is capable of generating severe earthquakes that would impact the entire west coast. Buildings could sustain extensive damage. Sherrod remembers his son, age 5 at the time, playing with toy trucks on the mossy banks of the marsh while the scientists worked. Shallow faults produce earthquakes in the upper 18 miles (30 kilometers) of the Earths crust. Johnson, on a whim, acquired the data that would prove its existence beyond a doubt. The Cascade block to the northeast is floored by diverse assemblages of pre-Tertiary rocks; the Coast Range block to the southwest is floored by lower Eocene marine basaltic rocks of the Crescent Formation. One model suggests it extends to about 30 miles east of Yakima. When this happens, even a very small slope can cause the ground to slide. Earthquakes on shallow faults typically last 20 to 60 seconds and the shaking is localized to the general area of the fault. The Cascadia subduction zone just off the Washington coast is this kind of fault and is one of the largest geologic hazards to our state. This scenario was modeled on the part of the SWIF from Woodinville to just west of Whidbey Island. They conclude the observed features have a glaciotectonic origin and are not seimotectonic. Drop to your hands and knees. He said scientists have known about the southern Whidbey fault for decades. Electricity, water, natural gas, and phones may not work. Someone screams. Faults can be grouped based on their relative movement into three types. Beef Barley and French Onion trenches cross the Little Bear Creek lineament. South Whidbey Island Fault (SWIF) M7.4 Earthquake Scenario Fire (Vegetation Condition Class) . Another big one is expected, and it could be devastating. Most injuries occur when people inside change rooms or try to leave the building. Southeast Extension of the Southern Whidbey Island Fault, Washington: Implications for Earthquake Hazards, 12201 Sunrise Valley Drive Reston, VA 20192, Region 2: South Atlantic-Gulf (Includes Puerto Rico and the U.S. Virgin Islands), Region 12: Pacific Islands (American Samoa, Hawaii, Guam, Commonwealth of the Northern Mariana Islands). These faults and earthquakes occur in the continental crust of North America. The trench did expose faults, but it was not possible to conclusively demonstrate offset of Holocene units. The Moment Magnitude Scale (M) measures the total amount of seismic energy (known as moment to engineers and seismologists) released by an earthquake. Seismic waves travel at hundreds to thousands of miles per hour and quickly reach the surface where they are felt or measured. In the area of North Bend, the fault zone is 4 miles wide and consists of a series of parallel faults. Unlike The Big One, scientists who have studied the southern Whidbey fault have far less understanding of when the next sudden shift might hit. The Pacific Tsunami Warning Center is located in Hawaii and is responsible for issuing alerts to all the countries that border the Pacific Ocean. Hold on to any sturdy shelter until the shaking stops. Stratigraphy and diatom assemblages of the marsh cores suggest Crockett Marsh underwent a 12 m of abrupt uplift relative to sea level at a time that relative sea level remained the same at Hancock Marsh. These combination faults are called oblique faults and include the Seattle fault, southern Whidbey Island fault zone, and DarringtonDevils Mountain fault zone. Get On The List To Receive Your Daily Dose Of Weird News And Amazing Phenomena. A paleoseismologist will look for surface ruptures along faults and may use carbon-14 dating to learn when the rupture happened. Landslide at Salmon Beach was triggered by the 1949 Tacoma earthquake and caused a tsunami. It forms the northern boundary of the Everett basin and lies along a series of high-amplitude aeromagnetic anomalies that extend from the Cascade Mountains to Vancouver Island, B.C. Gower (1980 #6229) showed and named the "southern Whidbey Island fault," and Gower and others (1985 #4725) showed this fault on their seismotectonic map of the Puget Sound region and briefly outlined its geologic relationships. These large underwater slides only occur during very large earthquakes and are one way to learn about earthquakes that happened thousands of years ago. Stop as quickly as safety permits and stay in the vehicle. Earthquakes cause damage by moving and shaking the ground, sometimes for several minutes. The crustal faults the Seattle Fault, the South Whidbey Island Fault, the Tacoma Fault those are less well known, said Forson. Clicking on the map will download the publication. California Department of Conservation. A major southern Whidbey quake, on the other hand, could kill and injure many more, according to Murphy. The height difference likely was caused by a 7.5 magnitude earthquake on the fault about 2,700 years ago, Sherrod said. Nearly all earthquakes occur on faults, features in the Earth where rocks move past each other. Out of these, the cookies that are categorized as necessary are stored on your browser as they are essential for the working of basic functionalities of the website. Ground shaking is a hazard near the epicenter of an earthquake and also in areas far from the earthquake where amplification occurs. This website uses cookies to improve your experience while you navigate through the website. Sensitive seismographs located throughout the state, and all over the world, measure this seismic energy. Source: United States Geological Survey. They didnt recognize the significance of what they found. Bending of the fault and transpressional deformation began during the late middle Eocene and continues to the present. Finding nothing of serious monetary value, the companies abandoned reams of information they had gathered through seismic surveys. Scientists are not sure how far east it goes. People are already fighting over toilet paper, just imagine what will it be like when they go shopping for food and the shelves are almost empty. People stagger into the streets to avoid an avalanche of debris. This map shows different seismic design categories that correlate with amount of seismic risk. By finding the age of the deformed layer, a paleoseismologist can determine the minimum age of the fault. All Rights Reserved 2021, Site Disclaimer A .gov website belongs to an official government organization in the United States. This was a problem because no two locations would agree on the size of the same earthquake. Superior Court:(800) 254-2755 Prepare to be on your own for at least three days. The 2011 Tohoku earthquake in Japan occurred on this type of fault and released enough energy to slightly change the Earths axis of rotation. At a downtown coffee shop, the mugs begin to chatter. The Eastern Sierra fault along the east side of the Sierra Nevada mountains in California is a good example of an active normal fault. Because they rupture at such great depth, their seismic energy is distributed over a large area. of Earth and Space Sciences, Box 351310, Univ. The below map shows that Seattle and its surroundings is constantly being rattled by small earthquakes and tremors. What are the most dangerous fault lines for Seattle? This fault will have an earthquake in the future, but we cannot predict exactly when. Discover in this article the most dangerous earthquake zones for Seattle and its area: The Cascadia Subduction Zone, the Seattle Fault and the South Whidbey Island Fault. Around Puget Sound, it seems everyone knows about The Big One, the potential magnitude 9.0 Cascadia Subduction Zone megaquake some scientists say is due any day. It is mandatory to procure user consent prior to running these cookies on your website. Once the shaking has stopped, exit the building if it is safe to do so. 552 - Hood Canal fault zone (Class B) 570 - Seattle fault zone 572 - Southern Whidbey Island fault zone 575 - Saddle Mountain faults 581 - Tacoma fault zone. 2 0 obj document.getElementById( "ak_js_1" ).setAttribute( "value", ( new Date() ).getTime() ); This site uses Akismet to reduce spam. North Anatolian Fault is currently locked, accumulating stresses which could be suddenly released anytime now like the Hayward Fault in California, Videos: New destructive M7.5 earthquake hits Turkey a few hours after largest quake in 100 years kills 1300. Photo by Steve Palmer. Close to shore, this same wave could reach heights of 30100 feet or more. Geologic maps of 7.5-minute topographic quadrangles covering parts of the Seattle fault and southern Whidbey Island fault zone are available on the DNR website as: Sign-up for DNR enewsletters. Theres approximately a 14% chance of another approximately M9 earthquake occurring in the next 50 years. A small quake was registered in the Coupeville area just this summer. The fault probably originated during the early Eocene as a dextral strike-slip fault along the eastern side of a continental-margin rift. And experts fear it could be even worse than The Big One.. Ready to retrofit? The Cascadia subduction zone last ruptured over 300 years ago on January 26, 1700. Scientists have also dated large underwater landslides and turbidites that travel from the continental edge far out into the ocean basin. Check out the liquefaction susceptibility and NEHRP site class maps on the Geologic Hazard Maps page. Audio; Before and After Images; Images; Slideshows; Stereograms; Videos; Webcams; . The Flying Squirrel and Mountain Beaver trenches cross the Cottage Lake lineament. For the most up-to-date information, please refer to the interactive fault map. But they didnt document it hardly at all.. Save my name, email, and website in this browser for the next time I comment. Doctor reveals the horrors Italian medics are facing in overwhelmed hospitals where dying patients are being left untreated as experts warn UK and US are just two weeks behind Italy and the public are not SCARED enough, An intensive care doctor in northern Italy has described the scale of the crisis Photo courtesy of National Center for Tsunami Research, NOAA. The southern Whidbey Island fault, and several others, were exposed for the first time from a camouflage of forest, ocean and glacial sediment. When a fault with vertical movement ruptures the ocean floor, it lifts up part of the ocean. A special type of shallow fault, called a subduction zone or megathrust, occurs where an oceanic plate moves beneath a continental plate. The bluff, where the cabins now sit, could have jutted up in the most recent Whidbey fault quake, Sherrod said. In 2017, he began studying the possible aftermath of a major SWIF quake. It usually also means that there are earthquakes (even small ones) on the fault. Stay away from glass, windows, outside doors and walls, and anything that could fall down. HomePrograms and ServicesGeologyGeologic Hazards. Earthquakes occur nearly every day in Washington. The team determined that the Rattlesnake Mountain fault zone, originally mapped by DNR geologist Tim Walsh in the 1980s, is likely the southern continuation of the southern Whidbey Island fault, extending this fault zone from the Strait of Juan de Fuca to Rattlesnake Mountain near North Bend. Strabge sounds very good report thanks a lot. We do not encourage people to evacuate in vehicles. Third, the South Whidbey Island Fault running from northwest to southeast of the southern tip of the island. Stratigraphy in the Flying Squirrel trench showed gentle warping of late glacial and post-glacial sediments; no faults were exposed. The tsunamis can travel far inland and deposit layers of sand and organic material. You just need one person to crash or a power line to fall over the road, and the roads are unusable.. Johnson and others (1996 #4751) described the structure and stratigraphy of the southern Whidbey Island fault zone. ; (5) large-scale liquefaction features in upper Quaternary sediments within the fault zone; and (6) minor historical seismicity. Armentrout, J. J. Miller, C. Finn, C. S. Weaver. In the 1990s, scientists producedan animationthat shows inundation, and people wont have much time to run to higher ground. The fault has at least three almost parallel strands within a 4- to 7-mile-wide band, stretching eastward from Vancouver Island. Earthquakes occur nearly every day in Washington. In general, larger faults make larger earthquakes. That place is the Ocosta School. This fault produces some of the largest and most damaging earthquakes in the world (M9). The friend obliged. Faulting produced warping at the site of greater than 2 m. Radiocarbon ages provide a maximum age for the folding event of 12,09011,670 cal yr BP. Consider whether earthquake insurance is right for you. Earthquakes can be measured in many ways, but the most accepted method is called moment magnitude. By sampling sediment from the marsh to the beach berm, Sherrod and his research partner, Harvey Kelsey, developed a timeline of the oceans climb. It devastated the coast of the Pacific Northwest and sent an orphan tsunami to Japan. <>/XObject<>/ExtGState<>/Pattern<>/ProcSet[/PDF/Text/ImageB/ImageC/ImageI] >>/MediaBox[ 0 0 612 792] /Contents 4 0 R/Group<>/Tabs/S/StructParents 0>> @\;L;=}%FC*l $@ 4x: 888O~xrsxx'/*rGRF\gI%~x(G-^-hjjq kx/V ou0hyegy0;ei`Tx&ilZ )TmZ$vb,`bQm|DR5x/ Strait of Juan de Fuca Fault Map The Puget Sound faults under the highly populated Seattle and Puget Sound region of Washington state form a regional network of interrelated seismologic geologic faults. Tap/click on "gear icon" for options and settings. Secure .gov websites use HTTPS If the epicenter is Everett, the SWIF could cause. The years have gone by. Recent geologic mapping by Washington State Department of Natural Resources (DNR) geologists reveals that this major fault zone extends through the Snoqualmie River valley in the vicinity of Carnation, Fall City, and North Bend. The buildings in this photo were built on soft materials that liquefied during the 1964 Niigata earthquake in Japan. Mapping along the Snoqualmie River valley also helped answer the important question of where the Seattle fault lies east of its last mapped position near Issaquah. Seattle Fault and Whidbey Faults HAZARD MAPS As part of the Hazard Mitigation Planning process, mapping of the hazards that have the potential to affect the jurisdiction is performed using geographic information systems (GIS) software. You can look at different geological hazard mapson the website of the Department of Natural Resources. Each year we map additional areas and learn more about existing faults and (or) discover new ones. The ground shaking from these earthquakes can last for several minutes. Johnson and others . The southern Whidbey fault is shallow, running right under Snohomish County as opposed to many miles off shore like the Cascadia fault. View Earthquake Map Faults Interactive fault map and comprehensive geologically based information on known or suspected active faults and folds in the United States. Finding faults and knowing how often they rupture is one of the most important tasks to keep society safe from these hazards. Large and damaging earthquakes are inevitable in Washington, but no one knows exactly when they will happen. People who look for evidence of past movement on faults are usually called paleoseismologists (from paleo-ancient and seismologist-one who studies earthquakes). Black lines show the South Whidbey Island Fault Zone, the Seattle Fault Zone and the Tacoma Fault Zone. A national credit rating service has improved its opinion of WhidbeyHealths financial future. The last time was 1,000 years ago between 900 and 903 A.D., said Forson. Make an emergency response plan for you and your family. Subtle scarps and topographic lineaments on Pleistocene surfaces are visible on high-resolution LiDAR topography at a number of locations (Sherrod and others, 2008 #7652); the northeast-side-up scarps exhibit 15 m of vertical relief, late glacial and post-glacial sediments (Sherrod and others, 2008 #7652). An earthquake occurs when rock inside the Earth moves or breaks. Experts believe a magnitude 9.0 could happen there anytime in the next 200 years or so. He said he believes dramatic shifts from that quake also may be visible on the western edge of Camano Island. In the late 1960s, speculators considered the Puget Sound region a frontier for petroleum exploration. A drill rig left of the blockade is collecting data about the failure. This is similar to how sound is quieter when you move away from a speaker. The plate that is forced down can have faults within it that still rupture and produce earthquakes. The 1964 M9.2 Alaska earthquake created a large tsunami from the fault rupture, and many smaller tsunamis from on-land and underwater landslides. But it didnt. What makes these faults mega is that the amount of energy released is hundreds to thousands of times more than almost any other type of fault. South Whidbey Island Fault Earthquake Scenario: 7.4 Magnitude Buildings Damaged: 320,776 Fatalities: 90 - 432 Injuries: 2,920 - 7,361 Economic Loss: $15,590,000,000 SeaTac Fault Earthquake Scenario: 7.2 Magnitude Buildings Damaged: 375,954 Fatalities: 16 - 123 Injuries: 1,394 - 3,404 Economic Loss: $13,400,000,000 Tacoma Fault Like other faults, when enough stress builds up, the megathrust will rupture. Additionally, because the continent moves up and over the ocean plate, large amounts of sea water are displaced and cause damaging tsunamis. This category only includes cookies that ensures basic functionalities and security features of the website. In this sense, the shaking of the ground is the sound of rocks breaking and moving deep within the Earth. Large earthquakes are likely to happen in Washington during your lifetime. The Cascadia Subduction Zone (also known as the CSZ) is a 700-mile long fault zone located off the western coastline of British Columbia, Washington, Oregon and northern California. In this photo, visitors to Green Lake Park near Seattle, Washington, have parked their bicycles as they look at the cracks made by the April 1949 earthquake. The material becomes so weak that it behaves more like a liquid than a solid. This earthquake caused parts of Restoration Point near on Bainbridge Island to be lifted 35 feet straight up. America is going to be punished just like the rest of the world. 12201 Sunrise Valley Drive Reston, VA 20192, Region 2: South Atlantic-Gulf (Includes Puerto Rico and the U.S. Virgin Islands), Region 12: Pacific Islands (American Samoa, Hawaii, Guam, Commonwealth of the Northern Mariana Islands), The southern Whidbey Island fault: An active structure in the Puget Lowland, Washington, S. Y. Johnson, C. J. Potter, J.M. Other faults are inactive and are left over from much older periods of deformation. Below you will find links to view and download hazard maps created for each jurisdiction included in the current mitigation planning process. So I think it is worth your time to learn more about the biggest seismic riskss and major fault lines criss-crossing this part of the Pacific Northwest, namely: Now lets visit the 3 most dangerous earthquake faults for Seattle one by one: The Cascadia Subduction Zone is a giant fault running from Cape Mendocino, Calif. past Oregon and Washington and doesnt end until its north of Vancouver Island in Canada. The French Onion trench exposed glaciolacustrine claystones, till, colluvial deposits, and Holocene soils. Over time, fault movement has created some interesting geologic features. The southern Whidbey Island fault should be considered capable of generating large earthquakes (Ms ?? Keaton and Perry (2006 #7653) excavated two trenches on the south end of the Brightwater treatment plant (KP1 site 572-3, and KP2 site 572-4). EVERETT The South Whidbey Island Fault is connected to a system of powerful earthquake fault lines stretching from Victoria, B.C., to Yakima that is capable of unleashing a devastating. Since their initial discovery, research has shown that the actual number of earthquakes is somewhere between 5 and 10 for each change in magnitude. Share sensitive information only on official, secure websites. After the shaking stopped the sand regained its strength. Story telling is an important part of the Native tradition and is how their history is passed down to the next generation. Radiocarbon ages of macrofossils constrain uplift timing to 2.83.2 ka. This can cause landslides to occur where they wouldnt normally happen. The threat to Puget Sound from a quake along the Cascadia Subduction Zone, off the coast of Washington, Oregon and California, is well documented. These older faults do not have any evidence for recent activity, but the Earth is always changing. Photo from, Liquefaction can be a big problem. When an earthquake happens there will not be time to google what you are supposed to do. and the Red Cross will be there to care for them. (1996) used seismic-reflection profiles in Puget Sound near Whidbey Island, sea-cliff exposures on Whidbey Island, and sparse borehole data to map and interpret the SWIF as a broad fault zone (6 to 11 km wide) dipping steeply to the northeast.